The present invention relates to door closure mechanisms, and more particularly to electrically actuated mechanisms for maintaining a door closed and for electrically releasing the door so that it may open.
Numerous latching mechanisms of this type have been developed, some of which consist of specially matched sets of hardware for mounting on both the door and its frame, and others of which mount only on the door frame and adapt it to receive a door having an existing non-electric mechanism. Typically, the actuation of such devices is effected by an electric solenoid, which retracts a latching member on the frame, or actuates a mechanism that releases a latching member from engagement with the mating structure mounted on the door.
One commonly used device of this sort is an electric strike such as that shown in U.S. Pat. No. 4,211,443 issued on July 8, 1980 to the Folger Adam Company. In that device, a keeper is rotatably mounted in a strike mechanism and is spring-biased to an outwardly-extending latched position. The opposite, or inside, face of the rotatable keeper has a curved surface leading to a step or abutment against which a pivoting arm rests to prevent rotation of the keeper, and a latch member normally secures the free end of the pivoting arm to prevent the arm from swinging away from the step. A solenoid retracts the latch and releases the keeper for rotation, so that when the solenoid is actuated and the door is simultaneously pulled, the keeper will rotate and release the door. The keeper, being spring biased, rotates back into a latching position once the door is opened. The keeper and housing are each of a heavy cast or forged metal construction.
This strike construction with a rotating keeper mounted in a strong housing prevents the strike from being pried into a release position, and also isolates the rather weak solenoid and pivot arm structure from the great forces which may sometimes be applied to a door closure. However, it essentially requires that the door-mounted portion of the latching mechanism, such as a post or fork, be retracted in order to reclose the door. This may require manual actuation of the door, which can be a nuisance when it is considered that a primary function of an electric strike is to permit remote control of an entry way.